Do you mean have the fan run 100% of the time instead of being cycled on/off by the engine computer? The reason it cycles on/off is to help ensure the car runs at the optimal temperature. Having it run all the time means it'll take longer for a cold engine to get up to normal operating temperature, and that will impact fuel economy and emissions.
Then again, if your fans aren't turning on at all and you've verified it's a problem with the computer and not the fans/wiring, and you can't/don't want to replace the computer, then wiring the fans to be on all the time is better than having no fans at all
Okay Chris. My fan runs on and off by the engine computer but I still experience some level of overheating especially within heavy traffic. On the highway, I don’t see anything like that but normal engine operations.
could that be the temperature sensor failing?
Is your overheating in the engine, transmission or both?
Whether it is your engine, transmission, or both, check these three things: confirm your coolant level is not low, that your thermostats are not stuck closed and that both fans are working. Get your car warmed up, with the AC on, and then, with the engine running, pull over and look under the hood:
1. Visually confirm that both fans are turning fast (you might need a good flashlight to see if they are spinning).
2. Using a glove and a rag, remove the radiator cap. It might spray and overflow a little bit, just be careful and make sure to not burn yourself on the hot water.
2a. Now that you've removed the cap, look at the coolant under the cap and verify that the coolant is flowing from the left side of the car to the right (into the radiator). If the car is fully warmed to operating temperature, the thermostats should open and the coolant show be flowing into the radiator. You can also probably tell by squeezing the radiator hose...you will feel coolant flowing through (again, it is 200+F, so wear a glove and be careful not to get burned).
2b. If the coolant level is low, then add coolant. You can just pour it in (you can use distilled water if you only need a bit, otherwise get some appropriate coolant from the auto parts store). I like to use a radiator funnel like this to pour it in: https://www.amazon.com/Lisle-24680-Spill-Free-Funnel/dp/B00A6AS6LY/
If the engine is overheating, and through the above tests you confirm that you are not low on coolant, that both fans are working and coolant is flowing through the radiator when the engine is hot, then I'd check to see if maybe the radiator is really dirty and not getting much airflow.
If it is the transmission overheating, then the problem might not be with your cooling system at all. It could be that one or both of your transmission fluid filters are clogged. The dealership normally replaces only one of the filters and don't tell you that there are two to replace. They both need to be replaced! Here is a DIY:
If your transmission is overheating, you should resolve the problem ASAP. Overheating your transmission will rapidly lead to a transmission failure that will cost more than the car is worth to repair.
John has given you a lot of good information. What I'll add is that if your car starts to overheat when idle but is normal when in motion then it suggests a problem with heat dissipation. The more obvious cause is non-functional cooling fans or the fans running but at too low a speed (they're multi-speed fans). However, it can also be a sign of a radiator no longer dissipating heat properly...they can and do go bad with age and when this happens you often get an overheating at idle situation. You won't see anything obviously wrong with the radiator, but it's still faulty.
If you have access to one of those instant heat thermometers let the car idle until the temperature gets above normal, then check the temperature of the upper and lower rad hoses. If the fans are running and you're not seeing an appreciable difference in the two temps, your radiator is no longer doing its job and should be replaced.
Thank you John and Chris. What I have observed are that, the car can idle for a longer period without overheating. It can travel very well on a Highway without overheating but when you drive at low speeds in town and within traffic, that’s when I can hear or see the coolant rushing in to the engine and boiling up within the reservoir. But on a higher speeds on a highway this does not happen when I stop to check. Besides both fans are working but I think their speeds must be checked for higher speeds
When you're driving at speed the air blowing through your radiator is keeping the coolant temperature reasonable, but when you're idling/driving slowly you don't have that airflow and the car overheats.
First thing to do is test the cooling fans. A good quality scan tool would be able to command the cooling fans to run at their different speeds...that would help determine if they're faulty or not. While it's true that turning on the AC will cause the fans to turn on it's not a perfect test. If the fans are only working at high speed (for AC) but not at the lower speeds the computer might be requesting when driving slowly, the AC test would make you think the fans are okay when they actually aren't.
If the fans are good then pull off the front fascia and see if the radiator is plugged up with leaves/dirt/debris and clean it out if necessary.
How long has it been since you replaced the coolant? If it hasn't been done in the last 5 years then drain it out, flush out the system, and put new coolant in to see if that helps.
If none of this helps the situation and it were me I'd then replace the radiator.